1. Field of the Invention
The present invention relates to a microwave oven, and in particular to a microwave oven which is capable of convection cooking and grill cooking by including an apparatus generating radiant heat and convection-performing the radiant heat inside of a cavity.
2. Description of the Prior Art
A microwave oven cooks foodstuff by utilizing molecular motion of the foodstuff which is generated by microwave.
The conventional microwave oven will now be described.
As depicted in FIG. 1, a door 15 having a transparent door screen 14 is installed on the front of the mainframe as hinged gate, a control panel 16 for setting functions and cooking time is installed on the side of the door 15.
The conventional microwave oven having convection cooking function will now be described.
As depicted in FIG. 2, there is a cooking cavity 2a having a certain area for cooking inside of the mainframe 1a, a magnetron 3 is installed on the outer side of the cavity 2a, a waveguide 17 is formed at the side of the magnetron 3 for guiding microwave inside of the cavity 2a.
A turntable 9 is placed on the inner bottom surface of the cavity 2a to be mounted on the food stuff, a motor shaft 8 is connected to the center portion of the bottom surface of the turntable 9, the motor shaft is extended outwardly and connected to a turntable operation motor 7.
A heater 18 covered by a heater chamber 19 generating heat for convection cooking is placed at the outer side of the cavity 2a, a blast fan 23 placed at the side of the heat chamber 19 for circulating the heat generated by the heater 18 inside of the cavity 2a is connected to a operating motor 20, a convection cooking table 24 is installed at the center portion of the cavity 2a so as to be removable.
Herein, a plurality of vent holes 22 are formed at the wall surface of the cavity 2a where the heater 18 is installed in order to circulate the heat of the heater 18 inside of the cavity 2a.
The convection microwave oven is mainly used to cook bread, in the cooking process, the bread is placed on the convection cooking table 24, the heater 18 and blast fan 23 operate to generate heat from the heater 18 and circulate the heat inside of the cavity 2a, and keep temperature inside of the cavity 2a uniformly while the bread is cooked.
The conventional grill cooking microwave oven will now be described. As depicted in FIG. 3, a cavity 2a having a certain area is formed inside of a mainframe 1a for cooking foodstuff, a magnetron 3 is installed at the outer side of the cavity 2a for generating microwave, a waveguide 17 is formed at the side of the magnetron for guiding microwave inside of the cavity 2a.
A turntable 9 is placed on the inner bottom surface of the cavity 2a to be mounted on the foodstuff, a motor shaft 8 is connected to the center bottom portion of the turntable 9, the motor shaft 8 is extended outwardly and connected to a turntable operation motor 7.
A heater 25 supported by a heater holder 24 is installed at the outer upper portion of the cavity 2a, a reflector 26 is installed at the outer upper portion of the cavity 2a adjacent to the heater 25 for reflecting the heat generated by the heater 25 inside of the cavity 2a.
The grill cooking microwave oven is mainly used to cook meat, in the cooking process, the meat is placed on the turntable 9, the heater operates to generate heat, the heat generated by the heater 25 and the reflected heat by the reflector 26 are transmitted inside of the cavity 2a.
However, in the above-mentioned convection cooking microwave oven, controlling the temperature inside of the cavity is difficult due to non-uniformity of heat distribution, because of the distance between the heater 18 and the foodstuff, portions adjacent to the heater 18 has high temperature, the opposite wall portion from the heater 18 has low temperature. In order to uniform the heat distribution, the blast fan 23 is installed at the side of the heater, but the circulated air flow interferes with the heat flow generated by the heater 18, accordingly the heat can not be transmitted properly to the opposite wall inside of the cavity 2a.
In addition, the conventional grill cooking microwave oven, non-uniformity of the heat distribution may occur because of the distance between the heater and the foodstuff, and it requires long time to get enough temperature inside of the cavity because it only uses convection heat transfer having limited 600.degree. C. surface temperature.
Furthermore, both heating apparatus are separately required for each convection cooking and grill cooking in the conventional microwave oven.